Hydropneumatic feed devices

ABSTRACT

A hydropneumatic feed device which includes a pneumatic cylinder; a hydraulic cylinder slidable in and constituting a piston for the pneumatic cylinder; a working member movable with the hydraulic cylinder; an arrangement for admitting pneumatic fluid to and exhausting it from the pneumatic cylinder to move the hydraulic cylinder through working and return strokes and thereby advance and retract the working member; a piston in the hydraulic cylinder; and an arrangement for controlling the flow of hydraulic fluid from one side of the last-mentioned piston to the other to regulate the rate of movement of the hydraulic cylinder during its forward and return strokes.

tent [191 Alexander et a1.

14 1 Apr. 30, 1974 1 HYDROPNEUMATIC FEED DEVICES [73] Assignee: Rockwell International Corporation,

Pittsburgh, Pa.

22 Filed: Jan. 29, 1971 211 App]. No.: 110,813

[52] US. Cl 92/12, 91/219, 91/300,

92/8 [51] Int. C1......; FlSb 15/22 [58] Field of Search 98/8, 9, 114, 113;

[56] I References Cited v UNITED STATES PATENTS 3,033,169 5/1962 Norwood 91/26 1,046,145 12/1912 Budesheim... 92/114 X 2,825,427 3/1958 Steibel 188/282 3,149,541 9/1964 Hutter et al. 92/8 3,302,533 2/1967 Hutter et al. 92/8 3,363,518 l/1968 Boissevain 188/319 3,559,776 2/1971 Schultze 188/319 Primary Examiner'Edgar W. Geoghegan Assistant ExaminerAllen M. Ostrager 5 7] ABSTRACT A hydropneumatic feed device which includes a pneumatic cylinder; a hydraulic cylinder slidable in and constituting a piston for the pneumatic cylinder; a working member movable with the hydraulic cylinder; an arrangement for admitting pneumatic fluid to and exhausting it from the pneumatic cylinder to move the hydraulic cylinder through working and return strokes and thereby advance and retract the working member; a piston in the hydraulic cylinder; and an arrangement forficontrolling the flow of hydraulic fluid from one side of the last-mentioned piston to the other to regulate the rate of movement of the hydraulic cylinder during its forward and return strokes.

11 Claims, 11 Drawing Figures mmmsom 1807.24

sfitU 2 BF 6 INVENTORS ROBERT H. ALEXANDER VINCENT J. KRAMER CECIL D. RINGER ATTORNEYS will 3 IF 6 INVENTORS ROBERT H. ALEXANDER VINCENT J. KRAMER CECIL D. RINGER m'marm m 1801.284

sum 5 or 6 INVENTORS 8 ROBERT H. ALEX ER VINC J. KRA

. RINGER ATTORNE PRTIEWR 30 m4 SHEET B 0F 6 INVENTORS ROBERT H. ALEXANDER VINCENT J. KRAMER CECIL o. RINGER Ma Maw TTORNE s HYDROPNEUMATIC FEED DEVICES,

This invention relates to hydropneumatic feed devices of a novel improved type.

Devices of the type with which the present invention is concerned are employed to advance and retract the cutting tool and/or workpiece in a variety of machines such as grinders, lathes, drill presses, planers, milling machines, etc. A typical device of this type utilizes a pneumatic cylinder as a motive power source and a hydraulic check to control or regulate the movement of the piston component of the pneumatic motor. Typically, the device is constructed to have a rapid advance during the first part of the feed stroke and then a slower feed rate and to have a rapid return stroke.

A number of hydropneumatic feed devices are commercially available, and many others have been described in the patent literature. Exemplary of these are the devices disclosed in US. Pat. Nos. 3,313,214 issued Apr. 1 1, 1967, for POWER FEED WITH LIQUID CHECK and 3,424,061 issued Jan. 28, 1969, for HY- DRAULIC CONTROL SYSTEM AND AIR CUSH- forth through working (or feed) and return strokes in the pneumatic cylinder. A working member fixed to and movable with the hydraulic cylinder is employed to impart the rectilinear movement tov a tool, workpiece, or the like.

Other important features of our invention are novel arrangements for adjusting the length of the rapid advance portion of the forward or feed stroke, for filling the hydraulic cylinder, and for accommodating changes in the volume of hydraulic fluid in the cylinder. Also, our invention includes a novel arrangement for controlling the flow of air to and from the pneumatic cylinder. This control arrangement has several advantages 'for example, it produces a back pressure in the exhaust side of the cylinder to increase the uniformity of movement of the hydraulic cylinder through its forward and return strokes and provides for a dwell period between the end of the forward and the start of the return strokes of the hydraulic cylinder and working member.

Air will typically be employed as the pneumatic operating fluid for the hydropneumatic feed devices we have invented. However. other pneumatic fluids may be employed, if desired. Accordingly, the reference to the pneumatic fluid as air" herein is to understood as being solely a convenience and not a limitation on the appended claims.

The primary object of the present invention has been identified above. Other important but more specific objects of the invention reside in the provision of novel, improved hydropneumatic feed devices:

l. which are adaptable for use with a variety of machine tools. I

2. in which the hydraulic check components are located in the pneumatic cylinder to reduce the bulk of'the device.

3. which are much simpler than heretofore proposed hydropneumatic feed devices such as those described in the above-identified US. Pat. No. 3,313,214, for example.

4. which are rugged, accurate, and versatile in the extent to which feed rates, length of rapid advance, and other operating characteristics can be adjusted.

5. which have various-combinations of the novel features and attributes identified above.

Other important objects and features and further advantages of the invention will become apparent from the appended claims and as the ensuing detailed description and discussion proceeds in conjunction with the accompanying drawing, in which:

FIG. 1 is a plan view of a hydropneumatic feed device constructed in accord with the principles of the present invention, part of an external cover being broken away to show certain internal components of the device;

FIG. 2 is a longitudinal section through the hy-' dropenumatic feed device of FIG. 1, taken substantially along line 22 of FIG. 1;

FIG. 3 is a right-hand end view of the hydropneumatic feed device of FIG. 1;

FIG. 4 is a section through a portion of the feed device to an enlarged scale;

FIG. 5 is a schematic layout of a valve arrangement in the head of a pneumatic cylinder employed in the hydropneumatic feed device of FIG. 1, the valves being in the forward or working stroke positions;

FIG. 6 is a view similar to FIG. 5, but with the valves in the return stroke or retract positions;

FIG. 7 is a horizontal section through a valve block employed to control the operation of the hydropneumatic feed device of FIG. 1;

FIG. 8 is a vertical section through the valve block;

FIG. 9 is a full scale longitudinal section through a stop pawl employed in the hydropneumatic device of FIG. 1;

FIG. 10 is a view of the pawl taken substantially along 1010 of FIG. 9; and

F IG. 1 1 is a circuit schematic for the hydropneumatic device of FIG. 1.

Referring now to the drawing, FIGS. 1-4 depict in detail a novel hydropneumatic feed device 20 constructed in accord with the principles of the present invention. Major components of this device include a pneumatic power cylinder 22 housing a hydraulic check cylinder 24 which forms the piston for the pneumatic cylinder and reciprocates a working member 26 through rectilinear forward and return strokes. The rate of movement of hydraulic cylinder 24 and working member 26 are governed by the rate of flow of hydraulic fluid through an unbiased piston 27 in the hydraulic cylinder.

Other major components of the device include an air I supply system 28 for the pneumatic cylinder located primarily in pneumatic cylinder head 30 (see FIGS. 5 and 6) and a control assembly 32 mounted on a housing 36. This housing is fixed to and extends longitudinally from pneumatic cylinder 22 in surrounding relationship to, working member 26.

Except as discussed below, pneumatic cylinder 22 is of conventional construction. This component of hydropneumatic feed device 20 includes a barrel 38 extending between and fixed to the cylinder head 30 reand 70'through1cover 34 as by screws 96.

ferr ed to above and a second pneumatic cylinderhead 40 as by tie bars 41 and retainers O ring 43 be tween cylinder head and barrel 38 andan O-ring 44 between the barrel and cylinder head 40 keep air from leaking to the exterior of the cylinder.

I Like pneumatic cylinder 22, the hydraulic cylinder 24 is for the most part of conventional construction. This component of hydropneumatic feed device 20 includes a barrel 46 into which cylinder heads 48 and 50 are threaded. An O-ring 52 between barrel '46 and cylinder head 48 and an O-ring 54 between the barrel and cylinder head 50 keep hydraulic fluid from leaking into pneumatic cylinder 22.

As shown in FIG. 2, the left-hand hydraulic cylinder head 48 is dimensioned for a sliding fit in the barrel 38 of penumatic' cylinder 22. The barrel 46 of the hydraulic cylinder is similarly dimensioned for a'sliding fit in pneumatic cylinder head 40. An O-ring 56 between hydraulic cylinder head 48 and pneumatic cylinder barrel 38 keeps air from leaking past cylinder head 48. A sec-.

ond O-ring 58 between pneumatic cylinder head-'40 and hydraulic cylinder barrel 46 keeps air from leaking to the exterior of hydropneumatic feed device 20.

the remainder of this, stroke at a relatively low rate of speed and that theythen move rapidlythrough the re- As will be apparent from the foregoing and from FIG. I

2,"hydraulic,cylinder 24c'onstitutes a piston for pneumaticj'cylinder 22.,Thatis, if air is admitted .to' the-lft hand end of the pneumatic cylinder as shown in FIG.

a forward or:working stroke. Conversely,'when air is admitted tothe right-hand side of the pneumatic'cylinder, hydraulic cylinder 24 will move to the left as shown in FIG. 2 through a retract or return stroke.

In. the illustrated embodiment of our invention as shown in FIGS. 1-4, working member 26 is a rack fixed to the'right-hand head 50 of hydraulic cylinder 24and extending from the latter into'housing 36.. Intermediate the ends of housing .36, the teeth 60 on rack 26 mesh with the teeth 62 on a pinion 64. Pinion 64 is formedv on a shaft'66 supported from the sidewalls 68 and 70 of housing 36 by'bearings72 and 74. The shaft'and bearingassemblage is retained in' place by a washer 84 and a 'retainerfr'ing 86.

2, hydraulic cylinder 24 willmove to the right through barrel 46. I

a Two flow passages '104 and 106 are formed through the piston. The first of these consists of a relatively large diameter aperture 108 communicating with a smaller diameter aperture 110. A shoulder 112 at the intersection of the two apertures provides a seat for a ball-"type check valve 114 kept in the larger of the two apertures 108"by a retaining'ring-ll6.. Asshown' in FIG. 4, ball 114 has a; considerably smaller diameter than the aperture 108 in whichit is located. Accordingly, when valve member 114 is displaced'away from seat 112, hydraulic fluid can flow through passage 104 fromlone side of piston 27 to theother. I The second flow passage v106 includesa.n, aperture 25 118 extending through piston-27. 'A second transverse aperture 120 intersects-aperture 118 in thehub 1220f Q the piston. Consequently, hydraulic fluid in cylinder 24 on the left-hand side of piston 27, for example, canflow through aperture 120 and then aperture'118 to the right-hand side of ,thelpistoni Referring still toFlG. 4., an 'elongatedcylindrical drawbar 124 is'threaded into the hub 122 of hydraulic piston 27. The rate-of flow of 'thehydraulic fluid through passage 106 is controlled by a needle typefluid metering valve 26 formed on the en of drawbar- 124 and disposed in aperture 118. The rate of fluid'flow through passage 106 can be varied by rotating drawbar I 12 4"r'elative'to hydraulic piston head 27 and thereby A drive hub 88 "is fixed to shaft 66 exteriorly of hou s- ,ing 36' by a' pin 90. Accordingly, as rack 26 is reciprocated by hydraulic cylinder24,-pinion 64, shaft 66 and hub '88 rotate firs't in one and then in the opposite direction -.as the direction of movement of the rack changes. This motion is utilized to move the cutting tool of or workpiece being processedby a tool of the type described abovef For example, hub 88 maybe employed to raise and lower the quill of a drill press.

displacing ne 1-" I To keep thepi'st'on from rotating fwhilelthe adjustment just'd'escribed made,an anti-rotation pin 128 is employed. This pin is secured in a recess 130 in. hydrau.

. lic cylinder head by a.reta ining' ringl32 Pin 128 is biased to the le'ft'as shown in FIG-4 byja' spring134in recess -130,between its blind,'innerend"and the antiro- To facilitate the assembly of hydropneumatic device 20 and to provide access to therack and pinion mechanism just described, housing 36 has a removable cover 34 as-mentioned above. This cover is attached to the sidewalls 68 and 70 of the housing as by screws 94.

Control assembly 32 is attached to housing sidewalls .68

Housing 36' also supports a Z-shaped bracket 98 (FIGS; 1'; and 3) which-is fixed to the housing as by screws 100. This bracket may be employed to support hydropneurnatic device 20 from the drill pressorother tool from which it is employed. I

. Referring now primarily to FIGS. 2 and 4, it will typi cally be desired that hydraulic cylinder 24 (and accordtation pin; The reduced diameter, left-hand end 136 'of the antirotation in piston27. I I

To adjust the rate-of-flow of hydraulic fluid through passage 106, hydraulic cylinder 24 is moved through the retract stroke to juxtapose cylinder head 50 with piston 27.. Drawbar 124 is then rotateduntil the lefthand end of antirotation pin 128 is engage'din recess 138 by spring 134. Rotation of drawbar124 is then continued until the desired adjustment of needle valve.

126 has been effected. A Nylok or similar frictional member 139 against valve 126 retains the valve in the position to which it is adjusted.

Referring now to FIG. 2, drawbar 124 rtehds to the exterior of hydropneumatic device 20 through hydraulic cylinder head 48 and pneumatic cylinder'head 30.

ingly rack 26) move through the initial part of the forward or feed stroke at-ahigh rate of speed and through Q-rings l 44 and 146 surrounding thedrawbar keep hydraulic fluid "and air from leaking past the-,drawbar through cylinder heads 48 and 30. Rotation of the drawbarto affect theadjustment ofneedle valve 126 just 'described, is made by rotatinga stop collar 140 dle valve 126 along passage" aperture pin isengagable in-a'recess138 formed fixed to the end of the drawbar as by a setscrew 142.

In addition to the antirotation mechanism just discussed, the right-hand head 50 of hydraulic cylinder 24 carries components for filling the hydraulic cylinder with fluid and for accommodating changes in the volume of hydraulic fluid in the cylinder.

More specifically, in the illustrated embodiment of our invention (see FIG. 4), rack 26 is fixed to hydraulic cylinder 24 by threading an externally threaded end portion '148 of the rack into a bore 150 extending through cylinder head 50 and having an internally threaded portion at its right-hand end. Seal 151 keeps fluid from leaking past this connection. A generally L- shaped passage 152 formed in rack 26 provides fluid communication between cylinder head bore 150 (and accordingly the interior of cylinder 24) and the exterior of the hydraulic cylinder. A conventional check valve type fitting 154 or the equivalent is threaded into rack 26 in communication with passage 152. Hydraulic fluid can be introduced into cylinder 24 through fitting 154, passage 152 in rack 26, and passage 150 in cylinder head 50. Access to fitting 154 is gained by removing a detachable cover 156' fixed over an aperture 158 in housing 36 as by screw 160.

As mentioned above, hydraulic head 50 also carries components for accommodating changes in the volume of hydraulic fluid in cylinder 24. Despite the various seals discussed above, hydraulic fluid may escape from cylinder 24 during the operation of hydropneumatic device 20. It is the function of the components just discussed to provide a reservoir for replacement fluid and to introduce this fluid into the main portion of the cylinder as hydraulic fluid is leaked therefrom or for other volume changes.

Referring now to FIG. 4, the reservoir for make-up fluid is a blind end bore 162 formed in cylinder head 50 and opening onto the interior of this cylinder. A piston 164 is secured in bore 162 by retaining ring 166. An O-ring 168 around piston 164 keeps hydraulic fluid from leakingpast it from the interior of cylinder 24 to the right-hand side of the'piston as shown in FIG. 4.

The volume change accommodating components also include a compression spring 170 in reservoir 162 in surrounding relationship to an indicator rod 172.

The indicator rod is fixed to piston 164 and extends through reservoir 162 and cylinder head 50 to the exterior of hydraulic cylinder 24.

In filling hydraulic cylinder 24, sufficient fluid is introduced into it to first fill the interior of the cylinder and to then move piston 164 to the right as shown in FIG. 4 against the bias exerted by spring 170. This fills reservoir 162. Indicator rod 172 moves to the right with piston 164, providing a visual indication from the exterior of the cylinder of the level of hydraulic fluid therein.

As hydraulic fluid escapes from cylinder 24 during the operation of device 20, compression spring 170 expands, biasing piston 164 to the left as shown in FIG. 4.'This transfers hydraulic fluid from reservoir 162 to the interior of the hydraulic cylinder to keep it full. As

the fluid in the hydraulic cylinder is replenished from reservoir 162, indicator rod 172 retracts into cylinder head 50, providing a visual indication of the decreasing level of fluid in the reservoir.

In addition to the components just discussed, the hydraulic check mechanism components of hydropneumatic feed device 20 include two stop arrangements for limiting the rectilinear movement of hydraulic piston 27. The first of these is a disclike member 174 fitted in a groove (not shown) in drawbar 124 between the lefthand head 30 of pneumatic cylinder 22 and the lefthand head 48 of hydraulic cylinder 24. A cooperating recess 176 in hydraulic cylinder head 48 allowshydraulic cylinder 24 to move to the left in pneumatic cylinder 22 until hydraulic cylinder head 48 abuts pneumatic cylinder head 30.

The second of the stop arrangements just mentioned includes the stop collar discussed above and a stop pawl 178. Stop pawl 178 is disposed in an internally threaded tube or cylinder 180. Tube 180 is threaded onto an externally threaded projection 182, which protrudes from the left-hand face of pneumatic cylinder head 30.

. As shown in FIGS. 9 and 10, stop pawl 178 has a circular right-hand portion 184 and a rectangular lefthand portion 185. A generally hour glass-shaped, rectangularly sectioned slot 186 extends through the pawl. Interrupted threads 188 are formed on one edge of the rectangular portion of the pawl.

Stop pawl 178 is assembled in sleeve 180 with interrupted threads 188 engaged in the internal threads in tube or sleeve 180. This retains the pawl in a selected position along the sleeve. Drawbar 124 extends through stop pawl slot 186 and is free to slide through the stop pawl until the latter is engaged by the stop collar 140 on the drawbar.

During the return stroke of hydropneumatic 'device 20, hydraulic piston 27 returns to a location determined by the engagement of fixed stop 174 with pneumatic cylinder head .30. The length of the stroke through which the piston moves in the forward or feed direction is limited by the engagement of hydraulic cylinder head 48 with pneumatic cylinder head 30. The length of the rapid advance portion of this stroke is adjusted by relocating stop pawl 178 along sleeve 180. To facilitate the adjustment of the stop pawl, an externally accessible handle 189 is provided. This handle is mounted on an elongated retainer 190 which extends through an elongated slot 191 in sleeve 180 (see FIG. 1) and is threaded into stop pawl 178. A compression spring 192 extending between the head 193 of retainer 190 and an internal shoulder 194 in handle 189 normally biases the handle towards sleeve 180. This clamps the sleeve between the stop pawl and handle 189 to retain the stop pawl in the position to which it is adjusted.

To adjust stop pawl 178 to a different position in sleeve 180, handle 189 is pulled outwardly against the bias of spring 192, and stop pawl 178 is rotated about drawbar 124 as shown by arrow 196 in FIG. 2 to disengage the interrupted threads 188 on the stop pawl from the internal threads in sleeve 180. The stop pawl is then slid along the drawbar to the desired new location, and handle 189 is released to re-engage the interrupted and internal threads and thereby retain the stop pawl inthe adjusted position. I

The operation of the hydraulic check mechanism just described can best be understood by reference toFIGS. 2 and 4. Turning then to these figures, it was pointed out above that the admission of air to the left-hand end of pneumatic cylinder 22 as shown in FIG. 2 will cause hydraulic cylinder 24 to move to the right in the pneumatic cylinder. Initially, hydraulic piston 27 moves to the right with the barrel 46 and heads 48 and 50,0f the hydraulic cylinder due to the absence of any restraining force on the piston. The advance is accordingly rapid. The rapid advance continues until stop collar 140 engages stop pawl 178. At this point, piston 27 can move no further.

Since the interior of hydraulic cylinder 24 is filled with an incompressible hydraulic fluid, the barrel and head components of the hydraulic cylinder can continue to move to the right only at a speed determined by the rate-of-flow of hydraulic fluid from the left to the right hand side of the piston through flow passage 106 once hydraulic piston 27 stops moving. 2 Since this is a relativelysmall passage and as it is partly obstructed by needle valve 126, the fluid flows slowly through the piston. The hydraulic cylinder barrel and heads and rack 26 consequently move only slowly to the right, the exact rate being determined by the position of metering valve 126. This is the feed portion of the forward or advance stroke in which the desired operation is performed on the workpiece being processed.

2 The pressure of the hydraulic fluid on the left-hand side of piston 27 during the forward stroke keeps ball-type valve 114 on seat 112 and thereby keeps hydraulic fluid from flowing to the right-hand side of the hydraulic piston through fluid passage 104.

I To return or retract hydraulic cylinder 24, air is admitted to the right-hand end of pneumatic cylinder 22. As was also mentioned above, this displaces the unit consisting of the barrel and heads of hydraulic cylinder 24 and rack 26 to the left as shown in FIG. 2. Again, due to the absence of any restraining force, piston 27 moves with the barrel and head components of the hydraulic cylinder and rack 26. The retraction accordingly proceeds at a rapid rate.

The hydraulic piston moves with the other components just mentioned until stop 174 engages pneumatic cylinder head 30, stopping the hydraulic piston in its original or initial position. When this occurs, the pressure generated on the right-hand side of the hydraulic piston -unseats ball valve 114, allowing the hydraulic fluid to flow rapidly through the relatively large passage 104 in the piston. Accordingly, the hydraulic piston and cylinder head assembly and rack 26 continue to move rapidly to the left to their initial positions.

The remaining major units of hydropneumatic device 20 are the air supply system 28 and control assembly 32. These control the flow of air to pneumatic cylinder 22 to extend and retract hydraulic cylinder 24 and rack 26 in the manner described above.

As shown in FIGS. and 6, the air flow controlling system 28 includes a pairof valves 197 and 198, which have stems-199 and 200 and are slidably mounted in bores 202 and 204. Those bores extend transversely through pneumatic cylinder head 30. O-rings 206 and 208 surrounding the heads 2l0'and 212 of the valves keep air from leaking past them to the exterior of the pneumatic cylinder.

The ends of bores 202 and 204 are closed by plugs 214, 216, 218, and 220. Each plug is surrounded by an O-ring type seal 222 and is retained in place in cylinder head 30 by a retainer ring 224. I

In a manner which will be explained below, depression of a start button 225 in control assembly 32 connects a source of pressurized air 226 through passages 227 and 228 in cylinder head 30 to the bores 202 and 204 through the cylinder head above valves 197 and 198. These bores and passages remain pressurized until one of two retract buttons 229 or 230 in the control assembly is depressedHThe air above valves 197 and 198 displaces them downwardly in bores 202 and 204 until valve portions 231 and 232 formed on stems 199 and 200 engage valve seats 233 and 234 formed in the bores (see FIG. 5).

With valves 197 and 198 positioned as shown in FIG. 5, air flows from source 226 through external lines 235 and 236 (FIG. 11) into a passage 237 in cylinder head 30. From here the air flows into the lower end of bore 202. The air continues from bore 202 through passages 238 and 240, around a ball-type check valve 242, and through passage 244 around needle valve 246 into the left-hand end of the pneumatic cylinder 22 as shown in FIG. 2.

At the same time, air trapped in the right-hand end of the pneumatic cylinder is exhausted through passages (not shown) in pneumatic cylinder head 40, external air conduit or tube 248, and fitting 250 into a passage 252 in pneumatic cylinder head 30. From here, the exhaust air flows past ball-type check valve 254 and a needle valve 256 in passage 258 and through a passage 262 into the bore 204 in which two-position valve 198 is located. With this valve in the forward stroke" position illustrated in FIG. 5, the exhaust air flows between a seat 264 formed in pneumatic cylinder head 30 and a valve member 266 fixed to the lower end of valve stem 200 as by washer 270 and-retainer 272 into the lower end of bore 204. From here the air is exhausted to the surrounding environment through passage 274.

3 There is a pressure drop across needle valve 256', and the fluid pressure in the passage 263 connecting passage 258 to passages 252 and 262 is consequently lower than the pressure in passage 252. This creates an imbalance of forces on check valve 254 which keeps it closed during the forward stroke of hydropneumatic feed device 20.

As will be apparent from the foregoing, with valves 197 and 198 positioned as shown in FIG. 5, air is supplied to the left-hand side of pneumatic cylinder 22 and exhausted from the right-hand side thereof. This creates an imbalance of forces on the left-hand head 48 of hydraulic cylinder 24, causing it to move to the right in pneumatic cylinder 22. This movement is controlled or regulated by the hydraulic check mechanism discussed above. 1

Referring again to FIG. 5, needle valve 256 is threaded into cylinder head 30 and surrounded by an O-ring 276.to keep air from leaking past it to the surrounding environment. V'alve256 has a slotted head 280, which permits it to be adjusted from the exterior of pneumatic cylinder 22. The needle valve is provided to restrict the flow of exhaust air through passage 274 and thereby create a back pressure on the right-hand side of left-hand hydraulic cylinder head 48 as the hydraulic cylinder moves through its forwardstroke. This limits the rate of movement of hydraulic cylinder 24 through pneumatic cylinder 22. This maximum rate of speed can be varied by adjusting needle valve 256 to increase or decrease the rate of exhaust air flow and thereby change the back pressure on hydraulic cylinder 24.

above that the manual start and retract buttons 225 and 229 and retract button 230 actuated to initiate the for ward and return strokes of hydropneumatic device 20 are incorporated in control assembly 32. More specifically, control assembly 32 includes a valve block 286 supplied with air from air. source 226 through lines 235 and 288 (see FIG. 11) and a fitting 290 threaded into Referring now to FIGS. 7 and 8, it was pointed out the valve block. The valve block is also connected to the air passages 227 and 228 in pneumatic cylinder head 30 above valves 197 and 198 through fitting 292, external line 294 (see FIG. 11), a fitting 295 fixed in the cylinder head, and cylinder head passage 296. The external lines or tubes 288 and 294 are connected by communicating passages 297, 298, 299, and 300 in the valve block.

Communication is established through the internal passages to admit air to passages 227 and 228 and thereby initiate the forward or feed stroke of hydropneumatic device 20 by depressing start button 225. More specifically, start button 225 is the actuator of a pilot valve 302, which includes a valve body 304 threaded into valve block 286. An O-ring 305 around the valve body keeps air from leaking past it to the exterior of the valve block.

Referring now specifically to FIG. 7, start button 225 is attached to a stem 308 slidably mounted in a bore 310 through valve body 304 and surrounded by an O- ring seal 311. A compression spring 312 biases start button 225 to the position shown in FIG. 7. In this position an O-ring 314 surrounding the inner end of valve stem 308 engages a seat 316 formed in the inner end of valve body 304. This keeps air in passage 298 from flowing 'into passage 299. However, when start button 225 is depressed, O-ring 314 is moved away from valve seat 316; and air can flow from passage 298, the bore 310 in valve body 304, and apertures 318 through the valve body into passages 299 and 300. From here, the air flows through the fluid circuits discussed previously into pneumatic cylinder head 30 to operate valves 197 and 198 to the FIG. position.

As will be apparent from the foregoing descriptions of start button 225 and the operation of hydropneumatic device 20, the start button is depressed to pressurize the appropriate passages in pneumatic cylinder head 30 and then released to trap the air in those passages.- Despite the various seals in the system discussed above, small amounts of air may leak from these passages. Accordingly, a make-up air passage 320 termi nating in a bleed orifice 322 communicating with passage 227 is provided in pneumatic cylinder head 30. As air escapes from the pressurized passages in the cylinder head, make-up air flows from passage 238 through passage 320 and bleed orifice 322 into passage 227 to replace the air lost from the pressurized fluid circuit.

The forward or feed movement of hydropneumatic device may be terminated and the return stroke initiated by depressing the manual retract button 229 incorporated in control assembly 32 and may also be terminated automatically by the depression of retract button 230. For example, in a typical application of the invention, hydropneumatic device 20 will be employed to advance and retract the quill of a drill press and will be supported from the frame of the drill press with retract button 230 oriented vertically as shown in FIG. 3. As the quill descends, the conventional depth stop screw of the drill press will engage and depress retract button 230. I

Retract button 230 is the actuator of a front stop pilot valve 328, which is essentially identical to the start valve 302 just described. Accordingly, the components of the two valves have been identified by the same reference characters except that those of valve 328 are followed by the letter a.

As shown in FIGS. 7 and 8, the valvebody 304a of stop valve 328 is disposed in a passage 330 in valve block 286. This passage communicates with the pas sage 299 described above through passage 332. When retract button 230 is depressed, O-ring valve member 314a is displaced away from the seat 316a in valve body 304a. This connects the pressurized passages 227 and 228 in the pneumatic cylinder head through passage 296, fitting 295, line 294, fitting 292, passages 300, 299, 332, and 330, bore 310a and aperture 318a in valve body 304a, and passages 334 and 336 to atmosphere. This allows the air in pneumatic cylinder head bores 202 and 204 above valves 197 and 198 to escape, reducing the pressure on the top sides of valves 197 and 198. There is line pressure in the bore 202 in which valve 197 is mounted and accordingly on the lower side of valve stem head 210. Also, there is line pressure on the bottom side of the valve stem head 212 of valve 198. This is because the section of bore 204 in which the bottom side of valve'stem head 212 is located is connected to pressurized air source 226 through passages 340, 341, and 342 in pneumatic cylinder head 30 and externallines 236 and 235. Accordingly, as the pressure above valves 197 and 198 decreases, the pressure of the air on the bottom sides of valve stem heads 210 and'212 creates an imbalance of forces on valves .197 and 198 which moves them upwardly until the valve member 266 engages the valve seat 264 formed in bore 204. Simultaneously, a valve member 344 secured to valve stem 199 by washer 345 and retainer 346 engages a similar seat 347 formed in the bore 202 through pneumatic cylinder head 30.

The rate at which the air escapes from above valves 197 and 198 is restricted by an adjustable needle valve 348 threaded into control assembly valve block 286 and surrounded by O-ring seal 349. Controlled release of the air from the tops of valves 197 and 198 provides a dwell period between the depression of front stop actuator button 230 and the start of the retract stroke in which hydraulic cylinder 48 and rack 26 do not move since there is not a sufficient imbalance of forces on valve stem heads 210 and 212 to move valves 197 and 198 from the FIG. 5 positions to the FIG. 6 positions until the pressure above valves 197 and 198 is reduced below that on the bottom sides of valve stem heads 210 and 212. The duration of the dwell can be changed by adjusting needle valve 348 to vary the bleed rate. The provision ofa dwell feature is important in drill press applications, for example, as it allows the drill bit to clean out the hole drilled before the retract stroke is initiated.

The seating of valve member 344 interrupts the communication between the lower end of bore 202 and passage 238 and accordingly terminates the flow of air to the left-hand side of pneumatic cylinder 22. And the seating of valve member 266 interrupts the connection from the bore 204 in which valve 198 is located to exhaust passage 274, isolating the right-hand end of pneumatic cylinder 30 from atmosphere. Alsowith valves 197 and 198 in the retract positions just described and illustrated in FIG. 6, air flows from air source 226 through external lines 235 and 236 and pneumatic cylinder head passages 342, 341, and 340 into bore 204. From here, the air flows past valve member 232, through passages 262 and 263 and past check valve 254 into passage 252. The air continues through fitting 250, line 248 and the above-mentioned passage (not shown) in pneumatic cylinder head 40 into the righthand end of the cylinder.

At the same time, the left-hand end of the cylinder is connected to atmosphere. More specifically, air flows from the left-hand end of the cylinder through passage 244, past needle valve 246, and through passages 240 and 238 into the bore 202 in which valve 197 is located. From this bore, the air from the left-hand side of pneumatic cylinder 22 is exhausted through passage 350 to the surrounding environment.

" Needle valve 246 performs the same back pressure providing function on the retract stroke that needle valve 256 does on the forward stroke. This valve is threaded into pneumatic cylinder head 30 and surrounded by O-ring seal. Slotted head 280a permits it to be adjusted from the exterior of pneumatic cylinder 22.

Consequently, with valves 197 and 198 in the FIG. 6

positions, there is a greater pressure on the right-hand side of hydraulic cylinder head 48 than on the left-hand side of the cylinder head. Hydraulic cylinder heads 48 and 50 and barrel 46 and rack 26 accordingly move to the left to the retracted position shown in FIG. 2. The air pressure on cylinder head 48 then keeps the cylinder head-barrel assembly and rack in the retracted position until start button 225 is again depressed to repeat the cycle.

During the retract stroke and while rack 26 and the hydraulic cylinder components with which it moves are in the retracted position, valve 198 is kept in its retract position as shown in FIG. 6 by line pressure applied to the lower side of valve stem head 212 through passage 340 and bore 204. Valve 197 is kept in its retract position as shown in the same Figure by line pressure applied to the bottom side of valve member 344 through passage 237 and the lower end of bore 202. When the start button 225 is depressed to repeat the cycle, however, both valves will move down to the forward positions shown in FIG. as the tops of valve stem heads 210 and 212 have larger areas than the bottom of valve 344 and the lower side of valve stem head 212.

The forward or feed movement of hydraulic cylinder 22 and rack 26 may also be stopped and the retract stroke initiated at any point along or at the end of the forward stroke by depressing the retract button 229 in control assembly 32. This button is the actuator of a pilot valve 354 generally identical to start valve 302. Accordingly, the components of these two valves have been identified by the same reference characters except that those of valve 354 are followed by the letter 12.

Depression of retract button 229 produces the same results as depression of front stop button 230. That is, when button 229 is depressed, the air trapped above valves 197 and 198 and keeping them in the forward stroke positions shown in FIG. 5 is exhausted to atmosphere through pneumatic cylinder head passages 227, 228, and 296, fitting 295, external line 294, fitting 292, and passages 300 and 299 in valve block 286 (apertures 318 in valve body 304 provide communication between the two sections of passage 299 traversed by the valve body). From here the exhaust air flows through the passage'356 in which the body 3045 of retract valve 354 is threaded, bore 3l0b in valve body 304b, and exhaustapertures 360. As discussed above in conjunction with the operation of front stop valve 328, relief of the pressure on the top sides of valve stem heads 210 and 212 results in a shift of valves 197 and 198 to the positions shown in FIG. 6 to effect retraction of hydraulic cylinder 24 and rack 26.

Many modifications may of course be made in the illustrated embodiment of the present invention without exceeding the scope thereof'For example, the manual start and stop valves do not have to be included in a control assembly mounted directly on hydropneumatic device 20 through its forward and retract strokes without employing his hands. 7 Suitable foot-operated valves are available from commercial sources.

It is accordingly not believed necessary to describe such valves herein, especially as their details are not part of the present invention.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which comewithin the meaning and range of equivalency of the claims are therefore intended to be embraced therein. i

What is claimed and desired to be secured by Letters Patent is:

l. A hydropneumatic device for advancing and retracting a working member, comprising: a pneumatic cylinder; a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; means including at least one valve for admitting a pneumatic fluid to'and exhausting it from the opposite ends of the pneumatic cylinder to move said hydraulic cylinder through said forward and return strokes and thereby extend and retract the working member relative to the pneumatic cylinder; and means for controlling the rate of movement of the hydraulic cylinder as it moves through its forward and return strokes, which comprises a piston slidable in said hydraulic cylinder, a sealreceiving recess extending around the periphery of the piston in the hydraulic cylinder, a seal confined in said recess for movement with the piston, said seal engaging said piston and the interior of the hydraulic cylinder to keep hydraulic fluid from flowing past said piston during both the. forward and return strokes, first and second independent flow passages through the hydraulic piston inwardly ofthe periphery thereof, and flow control means for permitting fiow through only one of said flow passages during the forward stroke of the hydraulic cylinder and for permitting flow through the other of said passages at a different rate during the return stroke, whereby said hydraulic cylinder may be caused to move at different speeds through at least selected portions of said forward and return strokes.

2. A hydropneumatic device for advancing and re tracting a working member, comprising: a. pneumatic 'cylinder; a hydraulic cylinder movable through forward and return strokes in'and constituting a piston for said. pneumatic cylinder; a working member movable with said hydraulic cylinder; means including at least one valve for admitting a pneumatic fluid to and exhausting it from the opposite ends of the pneumatic cylinder to move said hydraulic cylinder through said forward and return strokes and thereby extend and retract the working member relative to the pneumatic cylinder; means for controlling the rate of movement of the hydraulic cylinder as it moves through its forward and return strokes which comprises'a piston slidable in said hydraulic cylinder, at least one flow passage through said piston, valve means rotatablyv adjustable in said hydraulic pistonto vary the flow area through said flow passage, means providing a head for the hydraulic cylinder, and means for keeping the hydraulic piston from rotating in said cylinder while said valve means is adjusted comprising a recess in the hydraulic piston and a spring-loaded member supported by said cylinder head and extendible into said recess.

3. A hydropneumatic device for advancing and retracting a working member, comprising: a pneumatic cylinder; a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; means including at least one valve for admitting a pneumatic fluid to and exhausting it from the opposite ends of the pneumatic cylinder to move said hydraulic cylinder through said forward and return strokes and thereby extend and retract the work ing member relative to the pneumatic cylinder; means including a piston in said hydraulic cylinder for controlling the rate of movement of the hydraulic cylinder as it moves through its forward and return strokes; means providing a head for the hydraulic cylinder; a hydraulic fluid reservoir in said hydraulic cylinder head; and means for indicating the quantity of hydraulic fluid in said reservoir, said reservoir comprising a bore in said head communicating with the interior of said cylinder and said indicating means comprising a member having a piston portion in said bore and an indicator portion extending through said hydraulic cylinder head to the exterior of the hydropneumatic device and means biasing said member toward the interior of the hydraulic cylinder.

4. A hydropneumatic device for advancing and retracting a working member, comprising: a pneumatic cylinder having a head at one end thereof; a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder, said hydraulic cylinder having a head at the end thereof nearest the head of the pneumatic cylinder; a working member movable with said hydraulic cylinder; pneumatic fluid supply and exhaust means communicating with the interior of the pneumatic cylinder at opposite ends thereof, whereby the pneumatic fluid can be admitted to and exhausted from the pneumatic cylinder to move said hydraulic cylinder through said forward and return strokes and thereby extend and retract the working member relative to the pneumatic cylinder; means for controlling the flow of the pneumatic fluid through said pneumatic fluid supply and exhaust means; means including a piston in said hydraulic cylinder for controlling the rate of movement of the hydraulic cylinder as'it moves through its forward and return strokes, said piston having at least one passage for the flow of'. hydraulic liquid formed therethrough; and

means for adjusting the control over the rate of movement of the hydraulic cylinder exercised by the piston in the hydraulic cylinder comprising a control means including a valve member displaceable along said passage to vary the flow area therethrough, said control means extending through the hydraulic and pneumatic cylinders to the exterior of the latter and first and second sealing members surrounding and engaging the control means, said sealing members further engaging the cylinder heads of the pneumatic and hydraulic cylinders, respectively, to keep air in the pneumatic cylinder and hydraulic fluid in the hydraulic cylinder from leaking past the control means through the respective cylinder heads.

5. A hydropneumatic device for advancing a working member, comprising: a pneumatic cylinder having a cylinder head at one end thereof; a hydraulic cylinder movable in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; means for admitting pneumatic fluid to the pneumatic cylinder to move said hydraulic cylinder therealong and thereby extend the working member relative to the pneumati ccylinder and means for controlling the rate of movement of the hydraulic cylinder and the working member which comprises a hydraulic piston having a flow passage therethrough, said piston being movable in the hydraulic cylinder; a control member having a valve portion in said flow passage and fixed to said hydraulic piston for movement therewith for controlling the rate-of-flow of hydraulic fluid through said flow passage, said control member extending to the exterior of the hydropneumatic device; a first stop means fixed directly to said control member; and a second stop means exteriorly of and adjustable to different fixed positions relative to said pneumatic cylinder head, said first stop means being engageable with the second stop means to limit the movement of the control member and hydraulic piston relative to the pneumatic cylinder, whereby said hydraulic piston and cylinder can advance together and therefore at a relatively rapid rate until said first stop means engages said second stop means and whereby said hydraulic cylinder will thereafter advance at a slower rate determined by the rate-of-flow of the hydraulic fluid through the flow passage in the hydraulic piston.

6. The hydropneumatic device of claim 5, together with a tubular member surrounding said control member exteriorly of the pneumatic cylinder, said tubular member being fixed to the pneumatic cylinder head and said tubular member and said second stop means having cooperating means for retaining said second stop means in selected positions along said tubular member.

7. A hydropneumatic device for advancing a working member, comprising: a pneumatic cylinder having a cylinder head at one end thereof; a hydraulic cylinder movable in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; .means for admitting pneumatic fluid to the pneumatic cylinder to move said hydraulic cylinder therealong and thereby extend the working member relative to the pneumatic cylinder; and means for controlling the rate of movement of the hydraulic cylinder and the working member which comprises: a hydraulic piston having a flow passage therethrough, said piston being movable in the hydraulic cylinder; a control member having a valve portion in said flow passage,

said control member being fixed to said hydraulic pis-' ton for movement therewith to thereby control the rate-of-flow of hydraulic fluid through said flow passage and said control member extending to the exterior of the hydropneumatic device; a first stop means fixed to said control member; a second stop means exteriorly of and adjustable to different positions relative to said pneumatic cylinder head, said first stop means being engageable with the second stop means to limit the movement of the control member and hydraulic piston relative to the pneumatic cylinder, whereby said hydraulic piston and cylinder can advance together and therefore at a relatively rapid rate until said first stop means engages said second stop means and whereby said hydraulic cylinder will thereafter advance at a slower rate determined by the rate-of-flow of the hydraulic fluid through the flow passage in the hydraulic piston; a tubular member surrounding said control member exteriorly of the pneumatic cylinder, said tubular member being fixed to the pneumatic cylinder head and said tubular member and said second stop means having cooperating means for retaining said secnd stop means in selected positions along said tubular member, there being a bore in said second stop means through which the control member extends which has a cross-sectional dimension in one direction greater than the diameter of the control member, whereby said second stop means can be tilted relative to said control member, and said co-operating means comprising internal threads in the tubular member and interrupted threads on said second stop means engageable with saidinternal threads; and an actuator means accessible from the exterior of the tubular member for tilting said second stop means relative to said control member to disengage the threads on said stop means from the internal threads in said tubular member, whereby said second stop means can be shifted to a different position in said tubular member to vary the distances through which said hydraulic cylinder will advance at said rapid and slower rates.

8. A hydropneumatic device for advancing a working member, comprising: a pneumatic cylinder having a cylinder head at one end thereof; a hydraulic cylinder movable in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; means for admitting pneumatic fluid to the pneumatic cylinder to move said hydraulic cylinder therealong and thereby extend the working member relative to the pneumatic cylinder; and means for controlling the rate of movement of the hydraulic cylinder and the working member which comprises a hydraulic piston having a flow passage therethrough, said piston being movable in the hydraulic cylinder; a control member having a valve portion in said flow passage and fixed to said hydraulic piston for movement therewith for controlling the rate-of-flow of hydraulic fluid through said flow passage, said control member extending to the exterior of the hydropneumatic device; a first stop means fixed to said control member; a second stop means exteriorly of and adjustable to different positions relative to said pneumatic cylinder head, said first stop means being engageable with the second stop means to limit the movement of the control member and hydraulic piston relative to the pneumatic cylinder, whereby said hydraulic piston and cylinder can advance together and therefore at a relatively rapid rate until said first stop means engages said second stop means and whereby said hydraulic cylinder will thereafter advance at a slower rate determined by the rateof-flow of the hydraulic fluid through the flow passage in the hydraulic piston; a tubular member surrounding said control member exteriorly of the pneumatic cylinder, said tubular member being fixed to the pneumatic cylinder head and said tubular member and said second stop means having cooperating means for retaining said second stop means in selected positions along said tubular member, there being a bore in said second stop means through which the control member extends which has a cross-sectional dimension in one direction greater than the diameter of the control member, whereby said second stop means can be tilted relative to said control member, and said cooperating means comprising projections in the member surrounding the control member and means on said second stop means engageable with said internal projections; and an actuator means accessible from the exterior of the surrounding member for tilting said second stop means relative to said control member to disengage the means thereon from the projections in said tubular member, whereby said second stop means can be shifted to a different position in said tubular member.

9. A system for controlling the operation of a hydropneumatic device for advancing and retracting a working member which includes a pneumatic cylinder, a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder, and a working member movable with said hydraulic cylinder, said system comprising: means including a valve means and operable with said valve means in one position to admit a pneumatic fluid to one end of the pneumatic cylinder and to exhaust pneumatic fluid from the opposite end of the pneumatic cylinder and thereby move the hydraulic cylinder through its forward stroke and extend the working member relative to the pneumatic cylinder, said means being operable with said valve means in a second position to admit pneumatic fluid to said opposite end of said pneumatic cylinder and to exhaust it from said one end thereof and thereby move the hydraulic cylinder through its return stroke and retract the working member relative to the pneumatic cylinder; said means further being operable with said valve means in said first position to so apply pneumatic fluid to said valve means as to bias it toward said second position; a first means actuatable to so supply a pneumatic fluid to said valve means as to create thereon a pressure effective to move said valve means to said first position against said bias; a second means actuatable to bleed the pneumatic fluid from the valve means, whereby said valve means will be returned to said second position when sufficient fluid has been bled therefrom to reduce the pressure on the remaining fluid below that on the fluid exerting the bias on the valve means; and means for restricting the rate at which the fluid is bled from said valve means to postpone the reduction of pressure to the level at which the bias will return said valve means to said second position and thereby provide a dwell period between the actuation of said second means and the movement of said valve means to said second position in which there is no movement of said hydraulic cylinder or working member. I

10. A system for controlling the operation of a hydropneumatic device according to claim 9, together with an adjustable valve for selectively varying the rate at which the pneumatic fluid is bled from said valve means and thereby varying the duration of said dwell period.

1 1. A system for controlling the operation of a hydropneumatic device for advancing and retracting a working member which includes a pneumatic cylinder, a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder, and a working member movable with said hydraulic cylinder, said system comprising: pneumatic fluid supply and exhaust means communicating with the interior of the pneumatic cylinder at opposite ends thereof, whereby a pneumatic fluid can be admitted to and exhausted from the pneumatic cylinder to move said hydraulic cylinder through said forward and return strokes and thereby extend and retract the working member relative to the pneumatic cylinder; means for controlling the flow of the pneumatic fluid through the supply and exhaust means; means for controlling the rate of movement of the hydraulic cylinder as it moves through its forward and return strokes; and means automatically actuatable to stop the hydraulic cylinder prises valve means operable to cause said flow control- 17 18 and working member at a selected point of extension to and exhausted from the ends of the pneumatic cylinrelatwe to Sald pneumanc cylinder as sald hydrauhc der to one which will effect a retraction of said working cylinder moves through its forward stroke which commember relatlve to the pneumatic cylinder.

ling means to alter the pattern in which fluid is supplied v 7 Column 6, .Lines' 36 and 37, please delete "hydraulic cylinder head 48 with pneumatic cylinder head 30."

and insert in lieu thereof --stopcollar 140 with pawl l78.-'--

Column ll, Line 25, delete the numeral "22" and substitute the numeral -'-24--.

Signed and sealed this 10th day of December 1974.

(SEAL) Attest:

MCCOY H. GIBSQN, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents @27 3? I UNITED STATES PATENT OFFICE, CERTIFICATE OF CORRECTION Patent No. 3, 807,284 Dated April 30 1974 Inventor(s) Robert H. Alexander, Vincent J. Kramer, Cecil D. Ringer or appears in the above-identified patent It is certified that err corrected as shown below:

and that said LettersPatent are hereby 

1. A hydropneumatic device for advancing and retracting a working member, comprising: a pneumatic cylinder; a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; means including at least one valve for admitting a pneumatic fluid to and exhausting it from the opposite ends of the pneumatic cylinder to move said hydraulic cylinder through said forward and return strokes and thereby extend and retract the working member relative to the pneumatic cylinder; and means for controlling the rate of movement of the hydraulic cylinder as it moves through its forward and return strokes, which comprises a piston slidable in said hydraulic cylinder, a seal receiving recess extending around the periphery of the piston in the hydraulic cylinder, a seal confined in said recess for movement with the piston, said seal engaging said piston and the interior of the hydraulic cylinder to keep hydraulic fluid from flowing past said piston during both the forward and return strokes, first and second independent flow passages through the hydraulic piston inwardly of the periphery thereof, and flow control means for permitting flow through only one of said flow passages during the forward stroke of the hydraulic cylinder and for permitting flow through the other of said passages at a different rate during the return stroke, whereby said hydraulic cylinder may be caused to move at different speeds through at least selected portions of said forward and return strokes.
 2. A hydropneumatic device for advancing and retracting a working member, comprising: a pneumatic cylinder; a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; means including at least one valve for admitting a pneumatic fluid to and exhausting it from the opposite ends of the pneumatic cylinder to move said hydraulic cylinder through said forward and return strokes and thereby extend and retract the working member relative to the pneumatic cylinder; means for controlling the rate of movement of the hydraulic cylinder as it moves through its forward and return strokes which comprises a piston slidable in said hydraulic cylinder, at least one flow passage through said piston, valve means rotatably adjustable in said hydraulic piston to vary the flow area through said flow passage, means providing a head for the hydraulic cylinder, and means for keeping the hydraulic piston from rotating in said cylinder while said valve means is adjusted comprising a recess in the hydraulic piston and a spring-loaded member supported by said cylinder head and extendible into said recess.
 3. A hydropneumatic device for advAncing and retracting a working member, comprising: a pneumatic cylinder; a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; means including at least one valve for admitting a pneumatic fluid to and exhausting it from the opposite ends of the pneumatic cylinder to move said hydraulic cylinder through said forward and return strokes and thereby extend and retract the working member relative to the pneumatic cylinder; means including a piston in said hydraulic cylinder for controlling the rate of movement of the hydraulic cylinder as it moves through its forward and return strokes; means providing a head for the hydraulic cylinder; a hydraulic fluid reservoir in said hydraulic cylinder head; and means for indicating the quantity of hydraulic fluid in said reservoir, said reservoir comprising a bore in said head communicating with the interior of said cylinder and said indicating means comprising a member having a piston portion in said bore and an indicator portion extending through said hydraulic cylinder head to the exterior of the hydropneumatic device and means biasing said member toward the interior of the hydraulic cylinder.
 4. A hydropneumatic device for advancing and retracting a working member, comprising: a pneumatic cylinder having a head at one end thereof; a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder, said hydraulic cylinder having a head at the end thereof nearest the head of the pneumatic cylinder; a working member movable with said hydraulic cylinder; pneumatic fluid supply and exhaust means communicating with the interior of the pneumatic cylinder at opposite ends thereof, whereby the pneumatic fluid can be admitted to and exhausted from the pneumatic cylinder to move said hydraulic cylinder through said forward and return strokes and thereby extend and retract the working member relative to the pneumatic cylinder; means for controlling the flow of the pneumatic fluid through said pneumatic fluid supply and exhaust means; means including a piston in said hydraulic cylinder for controlling the rate of movement of the hydraulic cylinder as it moves through its forward and return strokes, said piston having at least one passage for the flow of hydraulic liquid formed therethrough; and means for adjusting the control over the rate of movement of the hydraulic cylinder exercised by the piston in the hydraulic cylinder comprising a control means including a valve member displaceable along said passage to vary the flow area therethrough, said control means extending through the hydraulic and pneumatic cylinders to the exterior of the latter and first and second sealing members surrounding and engaging the control means, said sealing members further engaging the cylinder heads of the pneumatic and hydraulic cylinders, respectively, to keep air in the pneumatic cylinder and hydraulic fluid in the hydraulic cylinder from leaking past the control means through the respective cylinder heads.
 5. A hydropneumatic device for advancing a working member, comprising: a pneumatic cylinder having a cylinder head at one end thereof; a hydraulic cylinder movable in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; means for admitting pneumatic fluid to the pneumatic cylinder to move said hydraulic cylinder therealong and thereby extend the working member relative to the pneumatic cylinder; and means for controlling the rate of movement of the hydraulic cylinder and the working member which comprises a hydraulic piston having a flow passage therethrough, said piston being movable in the hydraulic cylinder; a control member having a valve portion in said flow passage and fixed to said hydraulic piston for movement therewith for controlling the rate-of-flow of hydraulic fluid through said flow passage, said control member extendIng to the exterior of the hydropneumatic device; a first stop means fixed directly to said control member; and a second stop means exteriorly of and adjustable to different fixed positions relative to said pneumatic cylinder head, said first stop means being engageable with the second stop means to limit the movement of the control member and hydraulic piston relative to the pneumatic cylinder, whereby said hydraulic piston and cylinder can advance together and therefore at a relatively rapid rate until said first stop means engages said second stop means and whereby said hydraulic cylinder will thereafter advance at a slower rate determined by the rate-of-flow of the hydraulic fluid through the flow passage in the hydraulic piston.
 6. The hydropneumatic device of claim 5, together with a tubular member surrounding said control member exteriorly of the pneumatic cylinder, said tubular member being fixed to the pneumatic cylinder head and said tubular member and said second stop means having cooperating means for retaining said second stop means in selected positions along said tubular member.
 7. A hydropneumatic device for advancing a working member, comprising: a pneumatic cylinder having a cylinder head at one end thereof; a hydraulic cylinder movable in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; means for admitting pneumatic fluid to the pneumatic cylinder to move said hydraulic cylinder therealong and thereby extend the working member relative to the pneumatic cylinder; and means for controlling the rate of movement of the hydraulic cylinder and the working member which comprises: a hydraulic piston having a flow passage therethrough, said piston being movable in the hydraulic cylinder; a control member having a valve portion in said flow passage, said control member being fixed to said hydraulic piston for movement therewith to thereby control the rate-of-flow of hydraulic fluid through said flow passage and said control member extending to the exterior of the hydropneumatic device; a first stop means fixed to said control member; a second stop means exteriorly of and adjustable to different positions relative to said pneumatic cylinder head, said first stop means being engageable with the second stop means to limit the movement of the control member and hydraulic piston relative to the pneumatic cylinder, whereby said hydraulic piston and cylinder can advance together and therefore at a relatively rapid rate until said first stop means engages said second stop means and whereby said hydraulic cylinder will thereafter advance at a slower rate determined by the rate-of-flow of the hydraulic fluid through the flow passage in the hydraulic piston; a tubular member surrounding said control member exteriorly of the pneumatic cylinder, said tubular member being fixed to the pneumatic cylinder head and said tubular member and said second stop means having cooperating means for retaining said second stop means in selected positions along said tubular member, there being a bore in said second stop means through which the control member extends which has a cross-sectional dimension in one direction greater than the diameter of the control member, whereby said second stop means can be tilted relative to said control member, and said co-operating means comprising internal threads in the tubular member and interrupted threads on said second stop means engageable with said internal threads; and an actuator means accessible from the exterior of the tubular member for tilting said second stop means relative to said control member to disengage the threads on said stop means from the internal threads in said tubular member, whereby said second stop means can be shifted to a different position in said tubular member to vary the distances through which said hydraulic cylinder will advance at said rapid and slower rates.
 8. A hydropneumatic device for advancing a working member, comprising: a pneumatic cylinder having a cYlinder head at one end thereof; a hydraulic cylinder movable in and constituting a piston for said pneumatic cylinder; a working member movable with said hydraulic cylinder; means for admitting pneumatic fluid to the pneumatic cylinder to move said hydraulic cylinder therealong and thereby extend the working member relative to the pneumatic cylinder; and means for controlling the rate of movement of the hydraulic cylinder and the working member which comprises a hydraulic piston having a flow passage therethrough, said piston being movable in the hydraulic cylinder; a control member having a valve portion in said flow passage and fixed to said hydraulic piston for movement therewith for controlling the rate-of-flow of hydraulic fluid through said flow passage, said control member extending to the exterior of the hydropneumatic device; a first stop means fixed to said control member; a second stop means exteriorly of and adjustable to different positions relative to said pneumatic cylinder head, said first stop means being engageable with the second stop means to limit the movement of the control member and hydraulic piston relative to the pneumatic cylinder, whereby said hydraulic piston and cylinder can advance together and therefore at a relatively rapid rate until said first stop means engages said second stop means and whereby said hydraulic cylinder will thereafter advance at a slower rate determined by the rate-of-flow of the hydraulic fluid through the flow passage in the hydraulic piston; a tubular member surrounding said control member exteriorly of the pneumatic cylinder, said tubular member being fixed to the pneumatic cylinder head and said tubular member and said second stop means having cooperating means for retaining said second stop means in selected positions along said tubular member, there being a bore in said second stop means through which the control member extends which has a cross-sectional dimension in one direction greater than the diameter of the control member, whereby said second stop means can be tilted relative to said control member, and said cooperating means comprising projections in the member surrounding the control member and means on said second stop means engageable with said internal projections; and an actuator means accessible from the exterior of the surrounding member for tilting said second stop means relative to said control member to disengage the means thereon from the projections in said tubular member, whereby said second stop means can be shifted to a different position in said tubular member.
 9. A system for controlling the operation of a hydropneumatic device for advancing and retracting a working member which includes a pneumatic cylinder, a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder, and a working member movable with said hydraulic cylinder, said system comprising: means including a valve means and operable with said valve means in one position to admit a pneumatic fluid to one end of the pneumatic cylinder and to exhaust pneumatic fluid from the opposite end of the pneumatic cylinder and thereby move the hydraulic cylinder through its forward stroke and extend the working member relative to the pneumatic cylinder, said means being operable with said valve means in a second position to admit pneumatic fluid to said opposite end of said pneumatic cylinder and to exhaust it from said one end thereof and thereby move the hydraulic cylinder through its return stroke and retract the working member relative to the pneumatic cylinder; said means further being operable with said valve means in said first position to so apply pneumatic fluid to said valve means as to bias it toward said second position; a first means actuatable to so supply a pneumatic fluid to said valve means as to create thereon a pressure effective to move said valve means to said first position against said bias; a second means actuatable to bleed the pneumatic fluid from the valve meanS, whereby said valve means will be returned to said second position when sufficient fluid has been bled therefrom to reduce the pressure on the remaining fluid below that on the fluid exerting the bias on the valve means; and means for restricting the rate at which the fluid is bled from said valve means to postpone the reduction of pressure to the level at which the bias will return said valve means to said second position and thereby provide a dwell period between the actuation of said second means and the movement of said valve means to said second position in which there is no movement of said hydraulic cylinder or working member.
 10. A system for controlling the operation of a hydropneumatic device according to claim 9, together with an adjustable valve for selectively varying the rate at which the pneumatic fluid is bled from said valve means and thereby varying the duration of said dwell period.
 11. A system for controlling the operation of a hydropneumatic device for advancing and retracting a working member which includes a pneumatic cylinder, a hydraulic cylinder movable through forward and return strokes in and constituting a piston for said pneumatic cylinder, and a working member movable with said hydraulic cylinder, said system comprising: pneumatic fluid supply and exhaust means communicating with the interior of the pneumatic cylinder at opposite ends thereof, whereby a pneumatic fluid can be admitted to and exhausted from the pneumatic cylinder to move said hydraulic cylinder through said forward and return strokes and thereby extend and retract the working member relative to the pneumatic cylinder; means for controlling the flow of the pneumatic fluid through the supply and exhaust means; means for controlling the rate of movement of the hydraulic cylinder as it moves through its forward and return strokes; and means automatically actuatable to stop the hydraulic cylinder and working member at a selected point of extension relative to said pneumatic cylinder as said hydraulic cylinder moves through its forward stroke which comprises valve means operable to cause said flow controlling means to alter the pattern in which fluid is supplied to and exhausted from the ends of the pneumatic cylinder to one which will effect a retraction of said working member relative to the pneumatic cylinder. 